(1) Field of the Invention
The present invention relates to a method and an apparatus for etching the edge face of a semiconductor wafer in which only the edge face of the wafer having its peripheral edge chamfered is etched.
(2) Background Information
In the production of semiconductor wafers, a chamfering process is conducted wherein the edge face of a sliced wafer is chamfered by machining. By this chamfering process, the edge face tends to have a rough surface. If the edge face of the wafer is left in this condition, smears are likely to attach thereto, dust is likely to form, and thermal strain is likely to occur.
In order to smooth the edge face of such a machine-chamfered wafer, a process is performed wherein the edge face is treated by etching. To carry out such an etching treatment, a method is known wherein a plurality of wafers are directly laminated (Japanese Unexamined Patent Publication No. 134935/1987), and another method exists wherein wafers are first laminated while interposing a special spacer between them (Japanese Examined Patent Publication No. 57612/1991), and the laminated wafers are then dipped in an etching liquid such that only the edge face of the wafers are exposed so that only the chamfered portions are etched.
Although the edge face of a sliced wafer can be etched using these methods, the process of laminating multiple wafers is troublesome and is difficult to automate. Furthermore, when implementing these methods, the surface of one wafer is brought into contact with other wafers, and the wafers are likely to be damaged when they are peeled apart one by one.
In addressing these problems, one prior art apparatus has been proposed wherein a roller having a groove portion in which the edge face of the wafer may enter without making contact with the groove is utilized. An etching liquid is retained by surface tension within the groove portion of the roller, and the edge face of the wafer is brought into contact with the etching liquid to conduct the etching treatment. An apparatus of this type is disclosed in Japanese Unexamined Patent Publication No. 316936/1989. However, in this apparatus, it is difficult to retain the required amount of etching liquid by surface tension within the groove portion of the roller.
Furthermore, in order to provide a means for positionally orienting the wafer during use thereof, the typical semiconductor wafer is provided with an "orientation flat" formed by cutting off a part of the periphery thereof in a straight line. It is very difficult to control the prior art apparatus such that the edge face of the wafer can be brought into proper contact with the etching liquid while rotating the wafer without having the orientation flat of the wafer coming out of contact with the groove portion. Furthermore, it is impossible using this apparatus to etch the edge face of the wafer into a desired shape.